Electrically conducting compositions of doped polyphenylenes and shaped articles comprising the same

ABSTRACT

Electrically conducting doped poly(paraphenylene) compositions, and process of making such compositions, having direct current conductivities of at least 10 31  3 ohm -1  cm -1 , at room temperature, and up to 100 ohm -1  cm -1  and above; especially wherein the doping agent is a Group IA metal arene, a Group V halide, chlorine, bromine, or a mixture thereof; in particular potassium naphthalene, sodium naphthalene, AsF 5 , chlorine, or a mixture thereof. The polymers are useful as electronic devices, as substrates for electroplating, as materials for absorption of solar and of radio frequency radiation, and in general wherever electrical conductivity of the metallic type or of the semiconductor type, and light weight, are desired.

This application is a division of application Ser. No. 234,511, filed2/17/81, now U.S. Pat. No. 4,440,669 issued 4/3/84 which is acontinuation-in-part of our application Ser. No. 22,237, filed Mar. 20,1979, now abandoned and incorporates by reference the entire disclosurethereof except to the extent, if any, that the same may be inconsistantherewith.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electrically conducting compositions, usefulas electronic and optical materials, comprising a solid polymerpolyphenylene and as the doping agent to confer electrical conductivity,an electron donor or acceptor, or mixture thereof.

2. Brief Description of the Prior Art

The electronics industry is continuously searching for new and improvedmaterials for fabricating electronic components. Likewise, the plasticsindustry is in need of materials which have the property advantages ofconventional organic polymers, but which are also electricallyconducting. There is a special need in these industries for obtainingconducting materials exhibiting direct current conductivities of atleast about 10⁻³ ohm⁻¹ cm⁻¹, and preferably greater than one ohm⁻¹ cm⁻¹,which also have the desired processibility, mechanical properties, lowcost, and low density (i.e., light weight) characteristics of carbonbackbone organic polymers.

Conductivities referred to herein, unless otherwise specified, are asmeasured at room temperature.

Carbon backbone polymers, possessing conductive properties, can beprepared by pyrolyzing or graphitizing organic polymers, e.g. viadehydrogenation at elevated temperatures. Such resulting conductivity ismost likely due to the formation of electrically conducting graphiticstructures. However, such pyrolyzed or graphitized polymers aredifficult to prepare in a controlled fashion, and accordingly are likelyto exhibit undesirable variation in electrical properties; and are notconveniently processible.

The only non-pyrolyzed non-graphitic carbon backbone organic materialsknown to us with conductivities as high as 10⁻³ ohm⁻¹ cm⁻¹ are complexesof unsubstituted polyacetylene, --HC═CH--x, with specific electron donoror acceptor agents.

Researchers have tried for over twenty years to obtain highly conductingcomplexes of carbon backbone polymers. Recent efforts in the field todiscover substituted polyacetylenes which also form highly conductingcomplexes, comparable to those of unsubstituted polyacetylene, have notbeen successful.

Complexes of uncrosslinked polyacetylene with iodine, iodine chloride,iodine bromide, sodium, and arsenic pentafluoride having conductivitiesranging from that of the undoped polymers to between 50 to 560 ohm⁻¹cm⁻¹ at 25° C. have been described in J. Am. Chem. Soc. 100, 1013(1978). Also described therein are complexes of polyacetylene withhydrogen bromide, chlorine, and bromine having conductivities of up toat least between 7×10⁻⁴ and 0.5 ohm⁻¹ cm⁻¹, where the highestconductivity in this range is for the bromine complex. L. R. Anderson,G. P. Pez, and S. L. Hsu in J. Chem. Soc., Chemical Communications pp.1066-1067 (1978) describe bis(fluorosulfuryl) peroxide, FSO₂ OOSO₂ F, asa dopant for polyacetylene to produce a composition having a roomtemperature conductivity of about 700 ohm⁻¹ cm⁻¹. Also, the reference ofJ. Chem. Soc. Chem. Comm. 1979, p. 594-5 reports that poly-acetylenefilms electrochemically doped with aqueous KI solution or, Bu₄ NClO₄solution in methanylene chloride provide materials having roomtemperature conductivities of up to 970 ohm⁻¹ cm⁻¹. The possibleapplication of polyacetylene complexes as electronic devices isdescribed in App. Phys. Lett. 33, pp. 18-20 (1978).

Although such polyacetylene complexes are useful as electronicmaterials, they possess the disadvantages of environmental and thermalinstability of the matrix polyacetylene. For example, even in theabsence of oxygen, cis-polyacetylene transforms to trans-polyacetyleneat a rate of a few percent a day at room temperature, which could resultin a variation of electrical properties. Additionally, both isomers ofpolyacetylene readily react with oxygen, thereby changing the electronicproperties of either doped or undoped polymer. The infusibility andinsolubility of high molecular weight polyacetylene militates againstmelt or solution processing and the thermal reactivity in the form ofcrosslinking reactions also restricts or precludes the possibility ofmolding this polymer into shaped articles.

Certain charge transfer complexes of poly(p-phenylene) have beenreported, none having conductivity as high as 10⁻³ ohm⁻¹ cm⁻¹ (OrganicSemiconducting Polymers, J. E. Katon, Ed., 1968, p. 176).

In contrast to polyacetylene, poly(p-phenylene) although a conjugatedpolymer, has high thermal and oxidative stability. This polymer isstable at temperatures as high as 400° C. in air and 550° C. in inertatmospheres. Furthermore, poly (p-phenylene) exhibits exceptionalresistance to radiation damage, as described in J. Polym. Sci. A3, pp.4297-4298 (1965). Another advantage of poly(p-phenylene) is that objectshaving tensile strengths as high as 34,000 kPa (5000 psi) can be moldedfrom this polymer using powder-metallurgical forming techniques withoutchemical degradation of the polymer, as described in J. Applied Polym.Sci. 22 pp. 1955-1969 (1978). Previous efforts to obtainpoly(p-phenylene) complexes having conductivities as high as 10⁻³ ohm⁻¹cm⁻¹ have been unsuccessful. The highest reported room temperatureconductivity is 4×10⁻⁵ ohm⁻¹ cm⁻¹, which was obtained for apoly(p-phenylene) complex with iodine, as described in Polymer Preprints4, pp. 208-212 (1963). The temperature dependence of conductivity, σ, isgiven by the expression σ=σ₀ e^(-E/kT) where σ₀ is a material constant,k is Bolzmann's constant (8.6×10⁻⁵ eV/degree), T is temperature in °K,and E is the activation energy for conductivity. E is reported by theseauthors to have a value of 0.87 eV between room temperature and -100° C.By contrast, a much smaller temperature dependence is normally expectedfor a material to be a useful semiconductor. The above reference alsodescribes the formation of a complex between poly(pphenylene) andtetracyanoethylene. However, in this case the observed conductivity atroom temperature (10⁻¹¹ ohm⁻¹ cm⁻¹) is even lower than that observed forthe iodine complex.

SUMMARY OF THE INVENTION

We have unexpectedly discovered that electron donors and electronacceptors can be incorporated into polyphenylenes to produce novelmaterials having electrical conductivities which are continuouslyadjustable from 10⁻³ ohm⁻¹ cm⁻¹ to over 100 ohm⁻¹ cm⁻¹.

In accordance with this invention there is provided a compositioncomprising a solid polymer, consisting essentially of units havingpara-phenylene linkages, or of mixtures of such units with units havingmeta-phenylene linkages; and having incorporated therein an electrondonor or acceptor doping agent, or mixture thereof, wherein:

(a) the direct current conductivity of the composition incorporating theelectron donor agent alone is at least 10⁻³ ohm⁻¹ cm⁻¹ ; and

(b) the direct current conductivity of the composition incorporating theelectron acceptor agent alone, or in admixture with said electron donoragent, is at least 10⁻³ ohm⁻¹ cm⁻¹ ; said conductivities (a) and (b)being measured by the four-probe-in-line method at room temperature.

The direct current conductivity of certain compositions incorporating adoping agent can be controlled and reduced at least 5-fold and oftenmuch more, by adding a compensating agent to react with the dopingagent, such as a doping agent of opposite type or an agent which reactswith the doping agent; for example an electron donor reactive wth anelectron acceptor dopant; for instance ammonia or an amine acts as acompensator for AsF₅ dopant.

By "units having para-phenylene linkages" we mean units incorporatingthe para-phenylene structure, ##STR1## by "units having meta-phenylenelinkages" we mean units incorporating the meta-structure, ##STR2## andby "polymer" we mean a composition in which at least eight such unitsare connected together. A simple compound useable for purposes of ourinvention is the dimer, biphenyl, which we find behaves like a poly(p-phenylene) as shown in Example 9 below. Also illustrative of useablecompounds is phenanthrene of structure ##STR3## incorporating the tworings, designated "A" and "B" in the above formula, having similarlinkages to those of biphenyl. A simple compound having a mixture ofparaphenylene and meta-phenylene linkages is meta-terphenyl of structurewherein, as shown in Example 8, the two outer rings behave likep-phenylene units.

Mixtures of polymers can be used for purposes of our invention; and alsomixtures of appropriate polymers along with other compounds, such as inpitches, e.g. asphalt and residues from distillation of tars.

Preferred embodiments of our compositions are those wherein thepolyphenylene consists (at least in major part) of units havingpara-phenylene linkages, with the doping agent being an arsenical dopingagent such as arsenic pentafluoride, sodium or potassium naphthalene, orchlorine and being present in an amount of about 10⁻⁵ to 2 moles permole of phenylene units in said polymer. Certain preferred compositionshave direct current conductivities of at least 10⁻² ohm⁻¹ cm⁻¹ at roomtemperatures; some have values as high as 1, 10, and over 100.

Further provided is a shaped article of manufacture comprising theabove-described composition. Preferred embodiments of the shaped articleare an electrical conductor, a semiconductor, an n-p type junction, aninfrared radiation absorber, and a radio frequency radiation absorber.

Also provided is a process of making compositions of the invention.

DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS

The novelty of this invention is in the discovery that the electricalconductivity of polyphenylene can be surprisingly increased by theaddition of specific electron donor and/or electron acceptor agents, tovalues of about 10⁻³ ohm⁻¹ cm⁻¹ and greater, by incorporating into thepolymer an appropriate electron acceptor or donor doping agent, oradmixture of agents.

The reason why this result occurs is not clearly understood. A theorythat we do not wish to be bound by is that a "charge-transfer complex"is formed between the matrix polymer as host, and the incorporatedelectron donor or acceptor. This complex is strikingly different inelectrical properties as contrasted to a simple mixture of the polymerand agent. The complex behaves electrically as a semiconductor or ametal while a simple mixture with such agent mainly exhibits theelectrical properties of the matrix polymer, i.e. a non-conductor or aninsulator. Thus, the term "incorporated therein" does not include simplemixtures of polyphenylene and electron donors or acceptors, or mixturesthereof, wherein the conductivity is not at of polyphenylene andelectron donors or acceptors, or mixtures thereof, wherein theconductivity is not at least 10⁻³ ohm⁻¹ cm⁻¹. The appearance of opticalabsorption bands in the infrared, visible or ultraviolet regions in thedoped polymer, which are not present in the dopant or polyphenylenetaken separately, distinguishes between a simple mixture and achargetransfer complex.

A moderately large number of electron donor or acceptor agents willoperate to surprisingly increase the direct current conductivity ofpolyphenylene, as for example, arsenic pentafluoride, Group IA metalsand Group IA metal arenes. However, not all known doping agents areeffective. As illustrated by specific Example 5 below, bromine (a knownroom temperature agent for greatly increasing the conductivity ofpolyacetylene to greater than 100 ohm⁻¹ cm⁻¹) was found not effective atroom temperature in increasing the conductivity of polyphenylene even toa value as high as reported for iodine doping.

The reason for this is not clear. A theory that we do not wish to bebound by is that the incorporation of the doping agent intopolyphenylene results in the fractional ionization, e.g. sodium atom tosodium cation, of at least about ten mole percent of the incorporatedagent. This would be expected to lead then to formation of thecharge-transfer complex of particular structure resulting in a dramaticincrease in conductivity. One skilled in the art from this disclosurewill be able to very simply test particular electron donor or acceptoragents, or mixtures thereof, not specifically described herein, inpolyphenylene to determine if a dramatic increase in conductivityoccurs. Those resulting compositions incorporating an electron donoragent, and those compositions incorporating an acceptor agent, ormixture of donor and acceptor agents, having a direct currentconductivity of greater than about 10⁻³ ohm⁻¹ cm⁻¹, are regarded asbeing within the scope of the present invention. Surprisingly, chlorineand bromine are effective dopants at high temperature for polyphenyleneby this test, as illustrated by specific Examples below.

By the term "four-probe method", as used herein, is meant the known andaccepted art method of measuring the electrical conductivity of apolymeric film or material using either A.C. or D.C. current betweenfour contacts. A description of the four-probe method is made in J. Am.Chem. Soc. 100, pp. 1014-16 (1978), and hereby incorporated by referencefor that purpose. Specific details regarding the apparatus and procedureused are given in the Examples.

A preferred polymer from the viewpoint of obtaining the highestconductivities for the composition is essentially a solid, highmolecular weight poly(p-phenylene) i.e. a poly(p-phenylene) polymerconsisting essentially of units having para-phenylene linkages. By thisis meant that at least about 90 numerical percent of the structuralunits of the polymer are para-phenylene units. Also, such polymer shouldbe a solid and possess a sufficiently high molecular weight to beinsoluble in conventional solvents and infusible. The molecular weightcannot be reliably determined for high molecular weightpoly(p-phenylene) because of the insolubility and infusibility of thispolymer. The color of the high molecular weight poly(p-phenylene)polymer typically ranges from yellow to purple-black.

A wide variety of methods for synthesizing poly(p-phenylene) are wellknown. As an example, benzene polymerizes to poly(p-phenylene) undermild reaction conditions by various combinations of Lewis acid catalystsand oxidizing agents. A particularly efficient system is the aluminumchloride-cupric chloride system which provides poly(p-phenylene) in highyield after 0.5 hour at 35° C., as described in J. Am. Chem. Soc. 85,454-458 (1963). As described in J. Am. Chem. Soc. 81, pp. 448-452 (1959)dehydrogenation of poly(1,3-cyclohexadiene) yields poly(p-phenylene).Another method is via halogenation and pyrolysis ofpoly-1,3-cyclohexadiene (J. Pol. Sci. Part A, vol. 1 pp. 2057-2065 of1963 and vol. 3, pp. 1553-1565 of 1965). These and other methods knownin the art are suitable for preparing solid high molecular weightpoly(p-phenylene), characterized by insolubility in conventionalsolvents and infusibility, which consists essentially of paraphenylenelinkages.

A further aspect of the present invention is that the low molecularweight phenylene compounds including specifically biphenyl, p-terphenyl,m-terphenyl, p-quaterphenyl, p-quinquephenyl, and p-sexiphenyl undergoboth enhancement of conductivity and also polymerization, upon prolongedexposure to strong Lewis acids such as AsF₅. A particular utility ofsuch combined doping and polymerization process arises from the readyprocessibility in solution or in melt phase of the low molecular weightphenylene compounds (also called phenylene oligomers) having from 2 to 8phenylene units, whereby they can be put into a desired form, such asSchottky barrier diodes using n-type or p-type inorganic semiconductorsagainst a poly(p-phenylene) doped composition, obtained using suchphenylene oligomers and having metallic conductivity.

The above noted phenylene oligomers can be obtained, for example, by theaction of a sodium-potassium alloy on halogen derivatives of benzene,according to the method described in J. Polym. Sci. 16, 589-597 (1955).Other methods for synthesizing polyphenylene oligomers which are solubleand/or fusible are described in J. Macromol Sci. (Chem.), Al, 183-197(1967). The methods described therein utilize the cationicoxidation/polymerization or copolymerization of aromatic hydrocarbonssuch as m-terphenyl, biphenyl, and benzene. The processible p-phenyleneoligomers having from 2 to 8 para-phenylene units, doped with a dopingagent whereby the conductivity is at least 10⁻³ ohm⁻¹ cm⁻¹, formpreferred compositions of this invention.

Doping agents applicable in the subject compositions include electrondonor agents, which increase the inherent conductivity of polyphenyleneto a value of at least about 10⁻³ ohm⁻¹ cm⁻¹ and likewise acceptoragents or admixtures of donor and acceptor agents which increase theconductivity of polyphenylene to a value of at least about 10⁻³ ohm⁻¹cm⁻¹. Certain preferred compositions have direct current conductivity ofat least 10⁻² ohm⁻¹ cm⁻¹, at room temperatures, as measured by thefour-probe method; some values being as high as 1, 10, and over 100ohm⁻¹ cm⁻¹.

Representative examples of applicable doping agents include electrondonor agents such as Group IA metals, including lithium, sodium,potassium, rubidium, and cesium; and Group IA metal arenes, such assodium and potassium naphthalene, sodium and potassium biphenyl; andelectron acceptors such as Bronsted acids including HSO₃ F; non-metaloxides including SO₃ and N₂ O₅ ; Group V element sulfides including Sb₂S₅ ; and halides of metals of Groups VIB, VIII, IB , IIIA and VA;halides of inert gases; mixed halides; and fluorine-containingperoxides. Such halide dopants include SbCl₅, SbF₅, SbBr₃, CrO₂ Cl₂,CrO₂ F₂, SbF₃ Cl₂, AsF₅, XeF₄, XeOF₄, PF₅, BF₅, BCl₃, BCl₅, IF₅, HSO₃ Fand FSO₂ OOSO₂ F. Mixtures of dopants can be used and in some cases maybe necessary. (See Example 16 below). Preferred electron donor agentsare selected from the group consisting of Group IA metals and Group IAmetal arenes. Particularly preferred are sodium naphthalene andpotassium naphthalene. Preferred electron acceptor agents are the GroupVA element halides, particularly arsenic pentafluoride.

A further preferred dopant is chlorine, used at elevated temperatures.The type of conductivity conferred by chlorine is presently not known tous but does not appear to be due primarily to crosslinking since amaximum conductivity has been noted as the amount of chlorine used isincreased, beyond which the conductivity begins to decline as furtherincrements of chlorine are supplied. Fluorine, bromine and mixed halogensuch as ICl are also effective when elevated temperatures are usedduring doping.

Doping can be effected by contacting the agent in solution or in gasphase with the polymer, or electrochemically, as illustrated in theExamples below.

The type of dopant chosen depends upon the particular electroniccharacteristics desired in the resulting composition. For example whensemiconductors are desired, donor dopants, such as the Group IA metalsand Group IA metal arenes can provide n-type semiconductive material(electron conductivity) while acceptor dopants, such as AsF₅, canprovide p-type material (hole conductivity).

The interface between electron donor-doped and acceptor-dopedsemiconductive compositions provides an n-p junction which can serve,for example, as a rectifier. Such junctions can be provided by methodswell known in the art, such as by mechanically pressing together sheetsof n-doped and p-doped materials. Alternatively, one end of a sheet ofpolymer can be doped with a donor while the opposite end is doped withan acceptor, thereby providing an n-p junction at the interface betweenthese differently doped regions.

The concentration of conductor doping agent in the composition is fromabout 10⁻⁵ to 2 moles per mole of phenylene unit in the polymer. Thehighest conductivity is generally obtained by using either donor oracceptor dopants, rather than using a mixture of the two types. Theconductivity generally increases with increasing dopant concentrationand the highest obtainable dopant concentration normally corresponds tonot over about 2 moles of dopant per mole of phenylene units inpolyphenylene. The major conductivity increase in going from undopedpolyphenylene to the fully doped polymer generally occurs at less thanabout 5% of this value.

Various methods for incorporating the doping agent into polyphenylenecan be employed to form charge-transfer complexes. These methodsinclude, for example, exposure of the polymer in solid state or fused orin solution to a doping agent in the gaseous or vapor state or in liquidstate, neat or in solution, or by intimately commingling solidmaterials. Similarly, electrochemical reactions can be used for theformation of charge-transfer complexes of polyphenylene.

In general, temperatures not over 100° C., especially temperatures lessthan or equal to room temperature are advantageously employed,especially for highly oxidizing dopants such as arsenic pentafluorideand sulfonating agents. However, as above noted, doping by halogens isan exception to this rule. Use of these dopants should include annealingat elevated temperatures of at least 200° C., especially 450° to 800° C.When fluorine gas is the doping agent, it is desirable to supply thisgas initially not above 200° C., then to pump off the free fluorine gasremaining in the vapor phase and then to anneal the fluorine-dopedcomposition at a temperature reaching at least 450° C.

In general, where the doping agent is a gas or a solid, having anappreciable vapor pressure at room temperature, such as arsenicpentafluoride, it is preferred to contact the solid polyphenylene withthe doping agent in the gaseous or vapor state and preferably at reducedpressure. Where the doping agent is a solid at room temperature, havinglow vapor pressure, it is preferred to contact the polyphenylene with asolution of said doping agent in an inert solvent therefor.Representative solvents include diethyl ether, tetrahydrofuran and thelike. However, basic solvents, such as ammonia, are preferably excludedin acceptor doping if the highest conductivities are desired.

The rate of addition of the dopant in the vapor phase to thepolyphenylene is normally largely determined by the reaction temperatureand the concentration (or vapor pressure) of the dopant. This rate isnot crucial. However, if a complex having the optimized conductivity isrequired it is desirable to add the dopant at as slow a rate as isconsistent with desired rates of manufacture. This normally requiresreducing dopant concentration or gas pressure, reducing reactiontemperature, and for the case of electrochemical reaction, reducingcurrent flow from those values which provide maximum doping rate.

The dopant can be added to the polyphenylene either before, during, orafter fabrication of the polymer into the form used for a particularapplication. For solution and/or melt processible polyphenylenes,conventional polymer processing technology can be used to derive desiredforms including films and fibers for the polymer, wherein the dopant cangenerally be added before dissolution or melting of the polymer, duringthe solution or melt processing, or after the product shape is providedby the solution or melt processing. For the polyphenylenes which areinsoluble and infusible, pressure compaction or pressure sinteringtechniques can be used to fabricate this polymer into desired shapes, asdescribed in J. Appl. Polym. Sci. 22, pp. 1955-1969 (1978). Again, thedopant can in general be added either before, during, or after themolding process. However, for dopants which lack high temperaturestability, the post-molding doping process is preferred. This latterprocess can also provide materials which are conductive on the surfaceand insulating inside, if the time of dopant exposure is insufficientfor dopant diffusion into the bulk of the article.

A characteristic feature of preferred compositions of the presentinvention is that these compositions, rather than being black, likecompositions described in the prior art, are instead colored; forexample, a bronze-gold color for heavily doped potassium and sodiumcomplexes and a green-metallic color for heavily doped AsF₅ complexes.These colors, which generally differ from those of the undoped polymers,reflect the changed electronic structure of the materials.

We have unexpectedly found that polyphenylene doped with a highconcentration of AsF₅, of about 0.2 mole dopant per mole of phenyleneunit, has a much higher stability than the corresponding heavily-dopedAsF₅ complex of graphite. The reference, Materials Science andEngineering 31, 161-167 (1977) discloses that both Stage 1 and Stage 2complexes of AsF₅ with graphite decompose rapidly in air, accompanied bygross exfoliation and emission of fumes of white solids. Also, AsF₅-doped polyacetylene is highly sensitive to air exposure, which resultsin rapid formation of the cubic modification of As₂ O₃. By contrast, nofume emission or exfoliation is observed with the polyphenylene-AsF₅complex and only relatively slow changes occur in electricalconductivity.

Also a subject of this invention is a shaped article of manufacturecomprising the subject composition. Our discovery that polyphenyleneforms conductive charge transfer complexes with certain electronacceptors and certain electron donors permits the fabrication ofelectrical conductors, semiconductor devices, such as rectifying diodesand transistors, n-p junctions, using the subject compositions and thewellknown technologies of device fabrication from n-type and p-typematerials. The technology applied to the inorganic polymeric material,(SN)_(x), described in Appl. Phys. Lett. 33, pp. 812-814, (1978) herebyincorporated by reference, for the construction of Schottky barrierdevices, useful as solar cells, can be used to construct devices fromthe subject compositions. The subject compositions can function aseither the metallic or the semiconductor part of such ametal-semiconductor barrier device, depending upon the extent of dopingof the polymer. A major advantage of polyphenylene as a junctionmaterial in such applications, as compared with the inorganic polymer(SN)_(x), or the polyacetylene complexes described in Appl. Phys. Lett.33, pp. 18-20 (1978), lies in its unusually high thermal stability.

Also, highly conducting polyphenylene complexes are highly absorbingover a wide spectral region in the infrared region. Hence, thesematerials can be used as infrared absorbers as, for example, inprotective eyeglass and solar energy applications.

Also, since the subject compositions are conducting, they can be used asantistatic materials or devices, such as a shaped gasket inside the lidof a solvent can.

The conducting doped compositions strongly absorb radio frequency andmicrowave radiation, so they can be used to shield sensitive electricalcircuits from electromagnetic interference or to contain sources of suchradiation.

In addition, the doped polymers differ from the undoped polymers in thatdirect metal deposition thereon via electroplating is possible. Theconductivity resulting from the doping process can provide the currentcarrying capability required for electroplating.

EXAMPLES

Polyphenylene used in the Examples below was prepared by the oxidativecationic polymerization of benzene as described in J. Org. Chem. 29, pp.100-104 (1964) and hereby incorporated by reference for that purpose; orwas purchased, if so indicated below. Elemental and functional analysesfor the reaction product are in agreement with those described in theabove reference for a polyphenylene consisting essentially ofpara-phenylene units. Unless otherwise indicated, doping and measurementof conductivity, in the Examples below, was at room temperature.

EXAMPLE 1

This example describes the doping of poly(paraphenylene) with anelectron acceptor (AsF₅) to produce a highly conducting material.

One and one-half grams of poly(p-phenylene) in powder form, prepared asin the J. Org. Chem. reference above cited, was compressed into acylindrical pellet at 2.76×10⁵ kPa (40,000 psi) in a 2.54 cm (1")diameter stainless steel mold, removed from the mold, and annealed at400° C. under ultra-high purity, commercially obtained nitrogen gas for24 hours.

This annealing was only precautionary, to remove possible byproducts,and was found to have no substantial effect on the conductivity of thepoly(p-phenylene), before or after doping.

Four electrodes were formed by painting an electrically conductingcement, Electrodag™, on the flat surfaces of this disk in a collineararrangement 1 mm apart. Platinum wires were used to contact theseelectrodes, so that electrical conductivity could be continuouslymonitored, during a doping process, by the standard four-point probetechnique.

The sample was then placed in a heat-resistant borosilicate glass cellwith provisions for evacuation and for the introduction of dopants, andwith glass-metal seals to permit exit of wires connected to the fourelectrodes on the sample. The two outer electrodes were connected to adirect current source (Keithley Model 163). The center wires wereconnected to an electrometer (Keithley Model 616) for voltagemeasurement. This arrangement permitted continuous monitoring of thevoltage and current, from which electrical conductivity could becalculated by Ohm's Law.

The cell containing the sample was evacuated to about 5×10⁻⁶ torr(6.7×10⁻⁷ kPa). At this point the room temperature conductivity measuredfor the undoped polyphenylene pellet was about 3×10⁻¹² ohm⁻¹ cm⁻¹. TheAsF₅ was added to the conductivity cell in 22 equal increments of dopantduring a two day period, wherein each increment produced about a 3 torr(0.40 kPa) increase in pressure for the cell volume. The electricalconductivity of the polyphenylene progressively increased over the twoday period. During this time period the initial purple-black-metallicappearance of the compressed pellet changed to green-metallic. The finalroom temperature conductivity achieved after the 22th increment duringthe two day period was 130 ohm⁻¹ cm⁻¹. This conductivity is greater thanthat of the original polymer by a factor of about 10¹⁴. The conductivitydecreased slightly to about 120 ohm⁻¹ cm⁻¹ upon standing in dynamicvacuum overnight. The temperature dependence of conductivity wasmeasured down to 77° K., where the conductivity observed was 50 ohm⁻¹cm⁻¹. The observed temperature dependence from room temperature down to77° K. can be described by an Arrhenius expression wherein theactivation energy is calculated to be 0.01 eV.

EXAMPLE 2

This example describes the preparation of a highly conducting materialby treatment of polyphenylene with an electron donor, potassiumnaphthalene, and the control of such conductivity through subsequenttreatment with an electron acceptor, arsenic pentafluoride.

Poly(p-phenylene) powder, prepared as in Example 1, incorporating fourparallel platinum wires, was compressed into a 12 mm diameterdisc-shaped pellet at 8.27×10⁵ kPa (120,000 psi). The embedded wireswere exposed by cutting away portions of the solid pellet until theexposed portions were long enough to permit attachment to the four-pointprobe conductivity apparatus described in Example 1. After heating at400° C. for 24 hours under ultra high purity nitrogen gas, the wiredpellet was positioned in a glass cell as in Example 1 along with 0.8 gpowdered potassium naphthalene. The cell was evacuated and oxygen-freetetrahydrofuran (THF) admitted until the pellet was totally immersed inthe potassium naphthalene solution.

Conductivity in the pellet increased over a period of 96 hours until alevel of 7.2 ohm⁻¹ cm⁻¹ was attained. Washing the pellet, now abronze-gold color, thoroughly with THF and drying under vacuum did notaffect this conductivity value. The thoroughly washed pellet was thenexposed to arsenic pentafluoride at a pressure of 45 torr (6.0 kPa). Theconductivity value dropped to 0.57 ohm⁻¹ cm⁻¹ after 33 minutes, thenincreased once again to 44 ohm⁻¹ cm⁻¹ in two more hours.

The conductivity of the potassium treated poly(p-phenylene) decreasedslightly when the pellet was cooled to liquid nitrogen temperature. Thesubsequent treatment with arsenic pentafluoride gave a material whoseconductivity decreased from 44 ohm⁻¹ cm⁻¹ to 24 ohm⁻¹ cm⁻¹ when cooledto liquid nitrogen temperature.

EXAMPLE 3

Poly(p-phenylene) powder, prepared as in Example 1, was compressionmolded at 8.27×10⁵ kPa (120,000 psi) pressure into five differentcylindrical pellets, each 1.25 cm in diameter and about 0.1 cm thick.These pellets were annealed at 400° C. under dry nitrogen gas for 24hours and weighed after returning to room temperature. Electrodes wereapplied to one of the pellets (sample #1) as described in Example 1.This pellet was suspended in the conductivity apparatus by four platinumwires attached to the electrodes as described in Example 1. Theremaining four pellets were placed on a platinum screen support in theconductivity apparatus, which was evacuated to 10⁻⁶ torr (1.3×10⁻⁷ kPa).The conductivity of sample #1 (undoped) was about 10⁻¹² ohm⁻¹ cm⁻¹.Conductivities of the other samples were not measured prior to doping.

Arsenic pentafluoride, in the vapor form, was introduced into theconductivity apparatus at a pressure of 455 torr (60.7 kPa) and theconductivity was measured as a function of time after exposure to AsF₅.The results are listed below in Table I.

                  TABLE I                                                         ______________________________________                                        AsF.sub.5 Exposure Time                                                                        Conductivity,                                                (hours)          (ohm.sup.-1 cm.sup.-1)                                       ______________________________________                                        0                10.sup.-12                                                   0.1              0.27                                                         0.2              0.41                                                         0.5              0.70                                                         1.0              1.4                                                          2.0              5.5                                                          3.0              72.3                                                         4.0              140.3                                                        5.0              154.9                                                        ______________________________________                                    

After five hours of exposure to AsF₅, the cell was evacuated to 10⁻⁶torr (1.3×10⁻⁷). The conductivity decreased slightly on evacuation to145 ohm⁻¹ cm⁻¹ after 16 hours. The conductivity apparatus wastransferred to a nitrogen-filled glove bag. Samples 2 through 5 wereweighed and their conductivities measured in the glove bag. Results areshown below in Table II. The conductivities of the pellets were measuredusing a Jandel Engineering Ltd. four-point probe apparatus and theKeithley Voltmeter and current source.

                  TABLE II                                                        ______________________________________                                                                  Wt.                                                         Initial   Final   Fraction                                                                             Conductivity                                 Sample #                                                                              Wt. (g)   Wt. (g) AsF.sub.5                                                                            (ohm.sup.-1 cm.sup.-1)                       ______________________________________                                        1       0.13707    not measured                                                                              145                                            2       0.13581   0.20971 0.352  103                                          3       0.13775   0.24416 0.436  170                                          4       0.13968   0.20746 0.327  103                                          5       0.14030   0.22086 0.365  140                                          ______________________________________                                    

The average conductivity value was 132 ohm⁻¹ cm⁻¹. The average weightfraction of AsF₅ in the doped samples was 0.37; this corresponds to a0.21 mole fraction of AsF₅ in (C₆ H₄)_(x) or about one AsF₅ molecule perfour phenylene units. The conductivity of sample #1 was measured as afunction of time under exposure to laboratory air. No visible fumes orvisible exfoliation of the sample were observed during air exposure. Theconductivity results are listed below in Table III.

                  TABLE III                                                       ______________________________________                                                         Conductivity                                                 Air exposure time (h)                                                                          (ohm.sup.-1 cm.sup.-1)                                       ______________________________________                                        0                145                                                          0.3              143                                                          0.8              144                                                          1.0              138                                                          1.5              128                                                          2.5              112                                                          3.4               99                                                          4.0               90                                                          4.7               78                                                          5.0               75                                                          ______________________________________                                    

After a few hours exposure to air, droplets of an acidic liquid appearedon the surface of the pellet. After five hours, Sample #1 was dipped inwater for about 1 minute; the conductivity was unaffected.

EXAMPLE 4

The following example illustrates doping with a p-type and dopant andthen adding, as a compensating agent, an electron donor.

A 1.0 cm diameter×0.1 cm thick pellet of poly(p-phenylene) was preparedand used for conductivity measurement as described in Example 1. Afterannealing at 400° C. under nitrogen gas for 24 hours, the pellet wasexposed to AsF₅ vapor until the conductivity of the pellet increased to1.1×10⁻² ohm⁻ cm⁻¹. At this point the apparent activation energy forconductivity was 0.02 eV. The doped pellet was then exposed to ammoniagas. Within ten minutes the conductivity decreased to 1×10⁻⁸ ohm⁻¹ cm⁻¹.After evacuation of the cell to 10⁻⁵ torr, the conductivity furtherdecreased to 10⁻¹¹ ohm⁻¹ cm⁻¹.

EXAMPLE 5 (COMPARATIVE EXAMPLE)

The following example demonstrates that bromine does not form a highlyconducting complex with poly(p-phenylene) upon doping at roomtemperature.

A 2.54 cm (1") diameter by 0.1 cm thick poly(phenylene) pellet wasprepared by pressing 2 gm of poly(phenylene) at 2.8×10⁵ kPa (40,000psi). This pellet was annealed for 24 h at 400° C. under nitrogen gas.The electrode and sample configuration were the same as described inExample 1. After evacuation to 10⁻⁶ torr (1.3×10⁻⁷ kPa), theconductivity of the undoped sample was 6×10⁻¹² ohm⁻¹ cm⁻¹. Br₂ gas wasintroduced into the chamber, whereupon the conductivity rapidlyincreased to 10⁻⁷ ohm⁻¹ cm⁻¹. After 20 hours exposure to Br₂, theconductivity reached a peak value of 1.0×10⁻⁶ ohm⁻¹ cm⁻¹. After 40 hoursexposure to high vacuum, the conductivity decayed to 1.4×10⁻⁷ ohm⁻¹cm⁻¹. A temperature dependence was recorded at this point yielding acalculated activation energy for conductivity=0.3 eV.

EXAMPLE 6

This example describes the preparation of a highly conductive materialby treatment of poly(p-phenylene) with an electron donor (sodiumnaphthalene).

Poly(p-phenylene) powder, as prepared in Example 1, was compressed intoa disc-shaped pellet (12 mm in diameter, 1 mm thick) at 8.3×10⁵ kPa(120,000 psi). After heating at 400° C. for 24 h under high puritynitrogen gas, the metallic looking purple-colored pellet was placed inone leg of an H-shaped borosilicate glass cell. This cell is designed toallow irrigation of the pallet by a THF solution of sodium naphthaleneprepared by interacting sodium metal (0.1 g) with naphthalene (0.6 g) indry, O₂ -free THF in the other leg. After 24 h of contact with thepellet, the sodium naphthalene solution was filtered off and the pelletwashed in dry THF until no discoloration of the wash liquid occurred.Drying the pellet overnight under a vacuum of 5×10⁻⁶ torr (6.7×10⁻⁷ kPa)gave a golden-brown material which showed signs of swelling and flaking.Measurement of conductivity with an ohmmeter in a strictly controlleddry argon atmosphere gave a lower limit of 2×10⁻¹ ohm⁻¹ cm⁻¹ for theconductivity.

EXAMPLE 7

Two 4 mg KBr pellets were prepared by compression with an applied torqueof 23.7 N.m (210 inch-pound) in a MiniPress™ pellet-maker for infraredspectroscopy. One mg of poly(p-phenylene), prepared as in Example 1, wascompressed onto the surface of one of these pellets using the abovemolding conditions.

An IR spectrum was taken of the poly-(p-phenylene)/KBr pellet as thesample and the KBr pellet as the reference.

Both of these pellets were contacted with AsF₅ vapor using the samemethod as described in Example 1. An IR spectrum was again taken withpoly(p-phenylene/AsF₅ /KBr as the sample and KBr pellet as thereference. The spectrum for undoped poly(p-phenylene) was essentiallyidentical to that reported in J. Org. Chem., 29, pp. 100-104 (1964),with prominent vibrational transitions at 800, 1000, 1400 and 1480 cm⁻¹.These vibrational transitions are completely masked in the doped samplewhich shows large increases in infrared absorption over the range fromat least 4000 cm⁻¹ down to at least 200 cm⁻¹, which are the limits ofthe measurement. On exposure of the doped pellet to NH₃ vapor, theinfrared absorption dramatically decreased and the vibrationaltransitions associated with the undoped polymer reappeared. This effectis due to compensation of the AsF₅ acceptor by the NH₃ donor as inExample 4. This experiment demonstrates that the conductive complexstrongly absorbs over a broad band in the infrared, which indicates thatsuch materials can be used in applications requiring an infrared shield,such as in solar energy and optical applications.

Furthermore, the reversibility of the optical behavior demonstrates thatthe novel properties of the subject compositions do not arise because ofirreversible covalent bond formation, between a dopant species and thepolymer chains, such as the replacement of the chain hydrogens withhalogens. It is well known in the art that substitution reactions suchas sulfonation, nitration and halogenation will occur, forming stableproducts, if a highly oxidizing chemical is added at relatively hightemperature.

EXAMPLE 8

(A) The doping of p-quaterphenyl, the four phenylene unit oligomericcompound with the electron acceptor, AsF₅, gives a highly conductingmaterial.

A 12.7 mm (1/2") disc-shaped pellet of commercially obtainedp-quaterphenyl powder pressed at 8.3×10⁵ kPa (120,000 psi) was attachedto a four point conductivity-measuring apparatus, as described inExample 1. The conductivity cell containing the wired pellet wasevacuated to 5×10⁻⁶ torr (6.7×10⁻⁷ kPa), and then AsF₅ was introducedthroughout the vacuum line, including the conductivity cell to apressure of 7 torr (0.93 kPa). Almost immediately the pellet changedcolor from ivory to a light green, with an accompanying rise inconductivity. The contents of the vacuum line were condensed into thecell using liquid nitrogen and then the cell was allowed to warm to roomtemperature. The pellet's color deepened through dark green to ametallic purple; the conductivity of the pellet at this point was3.9×10⁻³ ohm⁻¹ cm⁻¹. After 30 minutes another 7 torr (0.93 kPa) pressureincrement of AsF₅ was introduced into the vacuum line and condensed intothe conductivity cell. After warming to room temperature the pellet hadblackened. The conductivity rose to 1.2×10⁻³ ohm⁻¹ cm⁻¹. After exposureunder these conditions for 18 hours the conductivity was 8.9 ohm⁻¹ cm⁻¹.Exposure to air or to (CH₃)₂ NH causes fading of the color and decreasein the conductivity of these doped compositions.

(B) Similar phenomena and even higher conductivities, up to 50 ohm⁻¹cm⁻, have been observed in our tests with p-terphenyl exposed to 400torr (53 kPa) pressure of AsF₅. Comparison of the IR spectrum of thedoped p-terphenyl (after reaction with (CH₃)₂ NH to "compensate" theAsF₅ dopant followed by heating at 400° C. to drive off unreactedterphenyl and compensated dopant) vs. p-terphenyl and poly(p-phenylene)shows evolution of the spectrum, upon doping the terphenyl, toward thatof the poly(p-phenylene). From the relative strength of the bands near800 cm⁻¹ and 765 cm⁻¹ (out-of-plane C-H vibrations of para-substitutedand monosubstituted phenyl rings) the constituents oligomers in thisdoped composition were determined to contain from 6 to 12 phenyleneunits, averaging about 9 phenylene units.

(C) Meta-terphenyl has also been found in our tests to become conductiveupon doping with AsF₅. Our studies indicate that the m-terphenyl ispolymerized simultaneously, probably into polymer chains linked via theouter phenyl rings, forming units having paraphenylene linkages andmeta-phenylene linkages, of the structure: ##STR4##

(D) We have also found that p-phenylene oligomers become conductive uponexposure to potassium in the manner of Example 2 above; but theresulting compositions show no evidence of polymerization.

(E) Similar results have been obtained in our tests with the phenyleneoligomers biphenyl (Example 9), p-terphenyl (Example 10),p-quinquephenyl (Example 11) and p-sexiphenyl.

EXAMPLE 9

This example describes the doping of biphenyl with an electron acceptor(AsF₅) to produce a highly conducting material.

Crystalline powder of biphenyl was commercially obtained (from AldrichChemical Co.). One-half gram of this powder was pressed into acylindrical pellet at about 480,000 kPa (70,000 psi) in a 1.27 cm (0.5inch) diameter stainless steel mold.

Four electrodes were formed on the flat surfaces of this disk bypainting thereon an electrically conducting graphite cement (availableas "Electrodag") in a collector arrangement 1 mm apart. Platinum wireswere used to contact these electrodes, so that throughout the subsequentdoping process electrical conductivity could be continuously monitored,using the standard four-point probe technique per Jour. Am. Chem. Soc.100 pp. 1014-16 (1978).

The sample was then placed in a heat resistant borosilicate glass cellwith provisions for evacuation and introduction of the dopant, and withglass-metal seals to permit exit of wires connected to the fourelectrodes on the sample. The two outer electrodes were connected to adirect current source (a Keithly Model 163 current source). The centerwires were connected to an electrometer (a Keithly Model 616electrometer) for voltage measurement. This arrangement permittedcontinuous monitoring of the voltage and current, from which electricalconductivity could be calculated by Ohm's Law.

The cell containing the sample was evacuated to about 5×10⁻⁶ torr(6.7×10⁻⁷ kPa). At this point the conductivity measured for the undopedbiphenyl pellet was less than 10⁻⁹ ohm⁻¹ cm⁻¹, i.e. this composition wasinsulating. Then AsF₅ was added to the conductivity cell until thepressure was about 600 torr (80.0 kPa). The electrical conductivityincreased as the addition of AsF₅ proceeded. The pellet, originally purewhite, turned first a light green then eventually a deep blue at thefinal maximum conductivity measurement of 1.4 ohm⁻¹ cm⁻¹.

EXAMPLE 10

This example describes the preparation of a highly conducting materialby doping p-terphenyl with an electron acceptor (AsF₅).

Laser grade crystalline powder of p-terphenyl was commercially obtained(from Eastman Kodak Co.). A pellet was formed and doped as in Example 9above. The conductivity of the resulting pellet, measured as in Example9, increased from less than 10⁻⁹ to 4.16 ohm⁻¹ cm⁻¹.

EXAMPLE 11

This example describes the doping of p-quinquephenyl with an electronacceptor (AsF₅) to produce a highly conducting material.

p-Quinquephenyl crystalline powder was commercially obtained (fromPfaltz & Bauer Inc.). A pellet was formed and doped as in Example 9above. The conductivity of the resulting pellet, measured as in Example9, increased from insulating to 5.79 ohm⁻¹ cm⁻¹.

EXAMPLE 12

This example describes the doping of poly(paraphenylene) with chlorineto produce a highly conducting material which is stable in air.

Poly(p-phenylene) was prepared as in Example 1 above.

A pellet of this poly(p-phenylene) was prepared as in Example 9 aboveand was annealed at 400° C. under ultra high purity commerciallyobtained nitrogen gas for 24 h. The annealed pellet of poly(p-phenylene)was placed in a glass cell which was evacuated to about 5×10⁻⁶ torr(6.7×10⁻⁷ kPa). The pressure in the cell was increased with chlorinegas, so that the mole ratio of chlorine to phenylene units in thepolyphenylene was about 3:1. The cell was closed off, the chlorine gaswas condensed using liquid nitrogen, and the cell was sealed using anoxygen/gas torch.

The sealed cell containing the poly(p-phenylene) pellet and chlorine gaswas heated at 500° C. for 24 h after which it was transferred to anargon-filled glove box where it was allowed to return to roomtemperature and where the conductivity, measured as in Example 9, wasfound to be 2.7×10⁻¹ ohm⁻¹ cm⁻¹.

The conductivity of the pellet was then measured in air, and showed nosignificant change. After six months in air the conductivity of thepellet was again measured and there was still no significant change inits conductivity.

EXAMPLE 13

This example describes the doping of poly(p-phenylene) with chlorine ata very low Cl₂ /phenylene mole ratio to produce a highly conductingmaterial which is stable in air.

The pellet was prepared and doped as in the previous Example 12, exceptthat the Cl₂ :phenylene mole ratio used was only 1:20.

After doping, the pellet had a conductivity of 1.35×10⁻² ohm⁻¹ cm⁻¹which has remained stable in air (viz. 1.32×10⁻² ohm⁻¹ cm⁻¹) after a oneyear period.

EXAMPLE 14

In this example a pellet pressed from powdered poly(p-phenylene) wasexposed to the vapors of fluorosulfonic acid (HSO₃ F). In like mannerpowder of poly(p-phenylene) was contacted with liquid HSO₃ F. In bothcases the color of the pellet and the powder changed and highlyconducting materials were produced.

A pressed pellet of poly(p-phenylene) one half inch (12.7 mm) diameterand one millimeter thick was placed in a glass tube which was evacuated.Vapors of fluorosulfonic acid were admitted to this tube and allowed tocontact the pellet freely for 24 hours at room temperature. At the endof this time the pellet of poly(p-phenylene) had changed color frompurple to metallic green. The conductivity of this pellet was measuredusing the standard four probe method. The poly(p-phenylene) pellet givesa conductivity of 0.4 ohm⁻¹ cm⁻¹.

In a second set of experiments fluorosulfonic acid was distilled intothe tube in enough quantity to cover the powder. After contact at roomtemperature for 16 hours the dark tan powder had turned black. Followingthorough removal of excess liquid under vacuum, the powder was put intoa drybox and pressed into a pellet, which was metallic green in color.Conductivity reading of this pellet gives 30 ohm⁻¹ cm⁻¹ at roomtemperature.

EXAMPLE 15

This example describes the doping of poly(p-phenylene) with fumingsulfuric acid to produce a highly conducting material.

Poly(p-phenylene) powder, prepared as in Example 1, was compressionmolded at about 827,000 kPa (120,000 psi) pressure into a cylindricalpellet 1.25 cm in diameter and 0.1 cm thick. This pellet was annealed at400° C. under dry nitrogen gas for 24 h, then placed in a glass cell onthe vacuum line under reduced pressure of 10⁻⁶ torr (1.3×10⁻⁷ kPa). Thesample was exposed to vapors of fuming sulfuric acid of 15 to 18% freeSO₃ content for seven hours, after which it had a conductivity of 1.82ohm⁻¹ cm⁻¹. The sample was then maintained under reduced pressure of10⁻⁶ torr (1.3×10⁻⁷ kPa) for 16 h. The conductivity had then decreasedto 0.81 ohm⁻¹ cm⁻¹.

EXAMPLE 16

In this example a conducting material was formed from poly(p-phenylene)upon treatment with a combination of gaseous reactants. Neither gasalone was capable of providing a highly conducting polymer by exposureof the poly(p-phenylene) thereto.

A rectangular bar (13 mm×5 mm×1 mm) of pressed poly(p-phenylene) powderwas heated in a stream of nitrogen gas for 24 hours at 400° C. Samplecolor was metallic purple-black. After this treatment four platinumwires were attached to the bar's surface with Electrodag® conductingcement. As in Example 9 above, the sample was connected to wires insidea glass cell which permits continuous monitoring of electricalconductivity of samples exposed therein to gaseous environments. Afterevacuation of the cell the sample was exposed to 50.6 kPatrifluoromethylhydrofluorite (CF₃ OF). After 16 hours there was nochange in sample color and no change in sample conductivity. At thistime boron trifluoride was introduced to a pressure level of 50.6 kPa,and was condensed into the cell. Over a 20-day period conductivity roseto 5 ohm⁻¹ cm⁻¹. The sample had become black.

EXAMPLE 7

This example describes the doping of poly(para-phenylene) with anelectron acceptor (SbCl₅) to produce a highly conducting material.

A 1.0 cm diameter by 0.1 cm thick pellet of poly(p-phenylene) wasprepared and used for conductivity measurement as described inExample 1. After annealing at 400° C. under nitrogen gas for 24 hours,the pellet was exposed to liquid SbCl₅ for one hour. The liquid SbCl₅was distilled out under vacuum. The pellet was dried under vacuum forthree hours at 10⁻⁵ torr (1.3×10⁻⁶ kPa). Using the four-probe method atroom temperature, a conductivity of 11.5 ohm⁻¹ cm⁻¹ was measured forthis pellet.

EXAMPLE 18

This example describes the doping of poly(p-phenylene) with bromine at500° C. to produce a highly conducting material.

Poly(p-phenylene) was prepared as in Example 1 above.

A pellet of this poly(p-phenylene) was prepared as in Example 1 aboveand was annealed at 400° C. under ultra high purity commerciallyobtained nitrogen gas for 24 h. The annealed pellet of poly(p-phenylene)was placed in a glass cell which was evacuated to about 5×10⁻⁶ torr(6.7×10⁻⁷ kPa). Bromine gas was introduced into the cell so that themole ratio of bromine to phenylene units in the polyphenylene was about1:3. The cell was closed off, the bromine gas was condensed using liquidnitrogen, and the cell was sealed using an oxygen/gas torch.

The sealed cell containing the poly(p-phenylene) pellet and bromine gaswas heated at 500° C. for 24 h, after which it was transferred to anargon-filled glove box where it was allowed to return to roomtemperature and where the conductivity was measured, using thefour-probe method, and found to be 3.0×10⁻¹ ohm⁻¹ cm⁻¹.

The conductivity of the pellet was then measured in air, and showed nosignificant change.

EXAMPLE 19

This example describes the production of a conducting polymer complex bythe doping of poly(p-phenylene) at room temperature with fluorinefollowed by a high temperature annealing.

A pellet of poly(p-phenylene) was prepared as in Example 1 above and wasannealed at 400° C. under ultra high purity, commercially obtainednitrogen gas for 24 h. The annealed pellet of poly(p-phenylene) wasplaced in a stainless steel cell which was evacuated to about 5×10⁻⁶torr (6.7×10⁻⁷ kPa). Fluorine gas was introduced into the cell so thatthe gain in weight due to the fluorine gas added was 20.2% based on theweight of the poly(p-phenylene).

The cell was then evacuated and the sample transferred into a Pyrex cellusing an argon-filled glove box. The conductivity measured at this pointusing the four-point probe technique was quite low (about 10⁻¹² ohm⁻¹cm⁻¹).

The Pyrex cell containing the fluorine-doped sample of poly(p-phenylene)was placed on a vacuum line where it was evacuated and sealed using anoxygen/gas torch. The sealed cell containing the fluorine-doped sampleof poly(p-phenylene) was heated at 500° C. for 24 h after which it wastransferred to an argon-filled glove box where it was allowed to returnto room temperature and where the conductivity was measured using thefour-probe method, and found to be 0.12 ohm⁻¹ cm⁻¹. Upon exposure of thesample to air, the conductivity decreased to 2.9×10⁻² ohm⁻¹ cm⁻¹.

EXAMPLE 20

Phenanthrene (C₁₄ H₁₀), when exposed to liquid AsF₅, becomes a highlyconducting polymeric material.

Phenanthrene powder was placed in a glass tube and evacuated thoroughly.One-third the molar amount of AsF₅ needed for molar equivalence with thephenanthrene sample was condensed into the tube at liquid nitrogentemperature and then warmed to -23° C. The phenanthrene darkens to agreen-black during this process. After addition of a total of one molarequivalent of AsF₅ in this manner, by two more condensations, the tubewas allowed to reach room temperature and held there for two hours.After thorough vacuum evacuation, the resulting black powder was pressedinto a pellet and the conductivity meaasured.

The purple-black pellet gives a conductivity of 0.53 ohm⁻¹ cm⁻¹.

EXAMPLE 21

This example describes the doping of phenanthrene with gaseous AsF₅, togive a conducting polymeric material.

A 12.7 mm (1/2") disc-shaped pellet of commercially obtainedphenanthrene powder pressed at 8.27×10⁵ kPa (120,000 psi) was placed ina glass tube on a vacuum line at reduced pressure of 5×10⁻⁶ torr(6.7×10⁻⁷ kPa), and then AsF₅ was introduced to give pressure of 7 torr(0.9 kPa). After 16 h of exposure under these conditions the samplechamber was evacuated to about 5×10⁻⁶ torr (6.7×10⁻⁷ kPa). Theconductivity of the resulting pellet was found to be 1.6×10⁻² ohm⁻¹cm⁻¹.

EXAMPLE 22

A sample of rod form coal tar pitch (Allied Chemical Lot. No. S/N 78316)was pulverised to a fine powder and placed in a glass tube, which wasevacuated. AsF₅ was admitted to the glass tube to a pressure of about 50kPa (about 1/2 atmosphere) and the reactants allowed to stand for 64hours. After thorough evacuation of the tube it was taken into a dryboxand a pellet pressed from the black solids. The conductivity of thispellet measures 10⁻³ ohm⁻¹ cm⁻¹.

Prior to doping, this coal tar pitch at room temperature is electricallyinsulating, similarly to undoped poly(p-phenylene).

EXAMPLE 23

Electrochemical Doping of Poly(p-phenylene) with BF₄ ⁻.

A 1/2" (12 mm) diameter pellet of poly(p-phenylene) was prepared as inExample 1. The pellet, fitted with a platinum wire to allow its use as acathode, was partially immersed in an electrolyte of 0.5M AgBF₄dissolved in acetonitrile. A platinum electrode served as anode to forman electrolytic cell.

10 volts was applied between the Pt anode and the Pt wire on the pellet.The current flowing in the external circuit was monitored with anelectrometer. Over a period of 65 min. the current increased from 6×10⁻⁵amp to 3×10⁻⁴ amp, which represents a total cell resistance, after the65 minute period, of 3×10⁴ ohms.

The cell resistance decreased to 200 ohms when electrical contact wasmade from the anode directly to a portion of the pellet surface that hadbeen submerged in the solution; indicating that most of the 3×10⁴ ohmsresistance, measured across the cell, was due to resistance between thePt anode and the pellet; and therefore, that the surface of the pellethad been made conductive by incorporation therein of doping agent viaelectrochemically doping the polymer most likely with the ion BF₄ ⁻.

We claim:
 1. A process for producing a composition having a direct current conductivity at least 10⁻³ ohm⁻¹ cm⁻¹ which comprises contacting a polymer consisting essentially of units having paraphenylene linkages or of mixtures of such units with units having meta-phenylene linkages with a halogenating agent selected from the group consisting of chlorine, fluorine and mixed halogens containing fluorine or chlorine or both, and annealing the resulting composition at temperatures at least 200° C. and not exceeding 800° C.
 2. Process of claim 1 wherein the annealing temperature is between 450° and 800° C.
 3. Process of claim 1 wherein the halogenating agent is chlorine or fluorine.
 4. Process of claim 1 comprising contacting the polyphenylene with fluorine gas at a temperature not above 200° C. and pumping off the free fluorine gas remaining in the vapor phase, then annealing the resulting fluorine-doped composition at temperature reaching at least 450° C.
 5. Process of claim 4 wherein the polyphenylene is poly(para-phenylene).
 6. Process of claim 3 wherein the polymer is a poly(para-phenylene) and the halogenating agent is chlorine.
 7. Process of claim 1 wherein the annealing temperature is about 500° C.
 8. Process of claim 1 wherein the polyphenylene contains at least 90% units having para-phenylene linkages. 